import com.sun.source.tree.Tree;

public class BinarySearchTree {

    static class TreeNode{
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int val){
            this.val = val;
        }
    }
    public TreeNode root;

    /**
     * 插入
     * @param key
     */
    public  void insert(int key){
        if(root == null){
            root = new TreeNode(key);
            return;
        }
        TreeNode parent = null;
        TreeNode cur = root;
        TreeNode node = new TreeNode(key);
        while (cur != null){
            if(cur.val > key){
                parent = cur;
                cur = cur.left;
            } else if(cur.val < key){
                parent = cur;
                cur = cur.right;
            } else {
                //不能插入两个相同的数据，直接返回
                return;
            }
        }

        if(key < parent.val){
            parent.left = node;
        } else {
            parent.right = node;
        }

    }

    /**
     * 查找
     * 时间复杂度：
     *          最好情况：O(logN)
     *          最坏情况：O(N)
     * @param key
     * @return
     */
    public TreeNode search(int key){
        if(root == null){
            return null;
        }
        TreeNode cur = root;
        while(cur != null){
            if(cur.val == key){
                return cur;
            } else if( cur.val < key){
                cur = cur.right;
            } else {
                cur = cur.left;
            }
        }
        return null;
    }

    public void remove(int key) {
        TreeNode cur = root;
        TreeNode parent = null;
        while (cur != null) {
            if(cur.val < key) {
                parent = cur;
                cur = cur.right;
            }else if(cur.val > key) {
                parent = cur;
                cur = cur.left;
            }else {
                removeNode(parent,cur);
                return;
            }
        }
    }

    private void removeNode(TreeNode parent, TreeNode cur) {
        if(cur.left == null){
            if(cur == root){
                root = cur.right;
            } else if(parent.left == cur){
                parent.left = cur.right;
            } else {
                parent.right = cur.right;
            }
        } else if(cur.right == null){
            if(cur == root) {
                root = cur.left;
            }else if(parent.left == cur) {
                parent.left = cur.left;
            }else {
                parent.right = cur.left;
            }
        } else {
             TreeNode targetParent = null;
             TreeNode target = cur.right;
             while(target != null){
                 targetParent = target;
                 target = target.left;
             }
            cur.val = target.val;
            if(targetParent.left == target) {
                targetParent.left = target.right;
            }else {
                targetParent.right = target.right;
            }
        }
    }

}

